It is often preferable to perform a surgery as a minimally invasive surgery (endoscopy or arthroscopy) rather than as an open surgery. Endoscopy and arthroscopy are performed through the use of portals. These portals, made through incisions in the skin and some portion of underlying tissue, are used to fill the abdomen with air, in the case of endoscopy, and the surgical space with fluid, in the case of arthroscopy.
For the duration of this disclosure minimally invasive surgery will be described as it pertains to arthroscopic surgery; however, it is seen that the disclosure extends into endoscopy as well as arthroscopy and the invention disclosed should not be limited to arthroscopy.
A cannula is a medical device having an internal passage (or “cannulation”). A cannula can be inserted into a body, often to create a pathway for elongated instruments to pass into and out of the surgical space. During arthroscopy, as mentioned before, fluid is inserted into the surgical space (such as the shoulder) in order to pressurize and distend the surgical space and improve visualization through the arthroscope. One reason a cannula is inserted into the portal is to prevent this fluid from escaping out of the body.
The cannula functions to prevent fluid from escaping from the surgical space while instruments are inserted through the passage in the cannula as well as when no instruments are located in the cannula. This is typically performed by incorporating a flexible dam with slits into the passage in the cannula.
Cannulas generally consist of a proximal end, an elongated cannulated body, and a distal end.
FIGS. 1a-1b and 2a-2b depict views of a prior art cannula. A typical cannula 100 is made of a rigid plastic while flexible dams 102a and 102b are incorporated into the proximal end of the device and held in place by cover 101. The rigidity of the cannula's elongated body 103 allows the device to simply be threaded using thread 104 through the portals in tissue 10 and positioned over a site, such as depicted in FIG. 2a. However, because this type of cannula has a large moment arm (MA), it has a tendency to tip over when instruments are inserted through it, as depicted in FIG. 2b. For this reason, cannula 100 often has to be held in place while inserting instruments through the device, which is not desirable.
FIGS. 3a-3b and 4 depict views of another approach. Cannula 200 is made of a flexible material, with a passage 219 along elongated body 201 and a flexible dam 205 is incorporated into passage 219 along elongated body 201. Thin dam 203 may be attached at the proximal end of cannula 200.
Flexible flanges 202 and 206 are found on the proximal and distal ends of the device, and the length of cannula 200 is approximately the thickness of the skin and some portion of underlying tissue. This device has a tendency to remain in place and upright during instrument insertion. However, the device is inserted through the portal using a non-standard method, which is not desirable. An example of a non-standard method may involve holding the distal end of cannula 200 with the jaws of a grasping tool, advancing the jaws of the grasping tool and the distal end of cannula 200 together into the portal, and opening the jaws of the grasping tool to release cannula 200 from the grasping tool after the distal end of cannula 200 exits the portal and can be detected visually by surgical personnel.